Derivative Financial Instruments - Net Gains (Losses) Recorded in the Consolidated Statements of Income Relating to Free-Standing Derivative Instruments Used For Customer Accommodation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ 46	$ 11	$ (88)	$ 361
Interest rate contracts | Contract revenue | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	12	12	19	26
Interest rate contracts | Credit portion of fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	1	(1)	16	(34)
Interest rate contracts | Interest rate lock commitments | Mortgage banking net revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	57	82	89	182
Commodity contracts | Contract revenue | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	6	4	11	7
Commodity contracts | Credit portion of fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(1)	0	0	(1)
Commodity contracts | Credit losses | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	0	(1)	0	(1)
Foreign exchange contracts | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(3)	(6)	(5)	8
Foreign exchange contracts | Contract revenue | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	16	14	30	26
Foreign exchange contracts | Contract revenue | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(2)	(3)	(1)	3
Foreign exchange contracts | Credit portion of fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ 0	$ 1	$ 0	$ (1)